In saturated-steam turbine installations, the wet steam issuing from the high-pressure action of the turbine is dried and then slightly superheated before it enters the low-pressure turbine. These steps are effected in water separators/superheaters by mats of wire netting or baffle plate walls, as described in Brown Boveri Mitteilungen, January 1976, volume 63, line 66, et seq.
The disadvantage of this arrangement is that the down-flow line between the high-pressure turbine and the water separator elements in the steam flow is exposed to a relatively high water content.
This condition inevitably promotes erosion and/or corrosion and creates undesirable pressure drops.
Moreover, when water surges and local high concentrations of moisture form, the moisture can no longer be separated out by the separator to a significant degree.
Furthermore, the efficiency of separation of water by mats of wire netting and baffle plate walls depends upon the flow velocity of the steam, upon the droplet size and upon the absolute level of the wetness treatment.
It is known to expose the aforementioned separator elements as uniformly as possible to steam either by flow resistances arranged upstream or downstream of the separator elements, according to European Pat. No. 0,005,225 B1, or by special design of the flow paths, according to Swiss Pat. No. 483,864.
Although the exposure to wetness can be partially evened out by these measures, water surges and water streaks remain, and the absolute magnitude of the mean wetness can therefore not be changed. In this connection, it is known that, at about 10% wetness, the pressure drop in the connecting lines between the high-pressure turbine and the water separator is about 3 times greater than in the case of dry steam.
It is also known from European Pat. No. 0,096,916 A1 to provide in a high-speed water separator, upstream of the deflection blades, a water preseparator which essentially consists of a continuous slit in the wall of the pipe elbow, which slit is overlapped by a cover plate which projects into the flow channel. Although this achieves a separation of the water flowing in the vicinity of the pipe wall, "peeling" of the wall wetness concentration can be only very small if, as intended, only water in laminar flow is to be dealt with.
It is the disadvantages of the known solutions mentioned above for which the invention provides a remedy.